Monday, November 22, 2010

Quantum time travel: Black hole not required: The mathematics of quantum theory says that the quantum state that describes them evolves both forwards and backwards in time. This odd state of affairs has led to some researchers claiming that the normal rules of causality don't apply, so things that happen in a quantum particle's future will affect its past.

One of the first people to show this was John Wheeler at Princeton University. He showed that the classic "double slit" experiment, where an unobserved photon passes through two slits simultaneously, can be affected by a measurement that takes place after the experiment is ostensibly finished.